Variable resistor



1963 M. F. MELVIN 3,090,024

VARIABLE RESISTOR Filed Oct. 28, 1960 2 Sheets-Sheet 1 i I I l INVEN TOR. Mvnou F. MELVIN BY f alwdwwz ull4 Affomcus y 4, 1963 M. F. MELVIN 3,090,024

VARIABLE, RESISTOR Filed Oct. 28. 1960 2 Sheets-Sheet 2 mm TV ma VM mF N O m M Fig. 13. BY I ,mzmdsmw Afforngus 3,090,024 VARIABLE RESISTOR Myron F. Melvin, 6767 Spring Brook, North Drive, Indianapolis, Ind. Fiied Oct. 2s, 1960, Set. No. 65,735 7 Claims. (Cl. 333-170) This invention relates generally to variable resistor construction and in particular to a variable resistor construction for use in low voltage control circuits and which is of a modular construction permitting its utilization in several different applications.

While resistance is inherent in electrical circuits, it is usually necessary for the designer to introduce certain additional amounts to accomplish the required objective. Often these resistor units are of the fixed variety, that is, their resistance value cannot be readily altered. In many instances the fixed resistor cannot fulfill the complete requirements of the circuit due to varying circumstances. Variation of the resistance value of the resistor may be necessary because of differences in voltage supplies, oper ating characteristics of other components, temperature and humidity variations and variable results desired by the user. Because of this, electrical circuits and particularly electronic circuitry have required rugged and dependable variable resistors.

There are many methods of providing the required variable resistance for various types of applications. Some early developments in this field are used today, virtually in their original form. The variable resistors presently available vary considerably in shape, resistance range, wattage, heat dissipation, etc. Because of these factors and because economical considerations vary widely for different types of applications, the variable resistor manufacturer must either specialize narrowly or must provide variable resistors of many basic types if he is to cover the broad market requirements. Because of the pressure to provide models usable over a wide range of applications, certain compromises must be made in the design which can adversely affect the performance of the structure on a particular application. In spite of such compromises, the manfacturer of a broad range of variable resistors is presented with obvious stocking problems and the cost of extra parts and operations in producing the various models.

The concept of the present invention is to provide a variable resistor which can meet as many specialized performance requirements as possible with a minimum change in component parts. The ideal design from a manufacturers standpoint would be one which permitted any type of end product resistor to be constructed from standard parts which are so versatile that a minimum of duplication would be necessary and any one of various types of resistors could be obtained by the adding or subtracting of parts in the assembly process. An approach to this modular type of construction in the medium power, low cost wire-wound category of variable resistors is made in the structure of the present invention. Within this category, two specific types of variable resistors are included in the scope of the present invention.

One type is the sensitivity control which is a screwdriver adjusted, wire wound control. The second type is the low to medium wattage wire wound control, usually actuated by a shaft and usually provided with a means for mounting the control on a panel. The sensitivity control is normally used in electrical or electronic assemblies, which for all practical purposes, would be adjusted only at the time the end product was built. The only added change in setting of the control might occur when a re pair operation would be required. Thus, smoothness of rotation of the rotor and other similar considerations would be of little importance and would only increase the cost of the structure.

The second type, the shaft adjusted control, is a more finished unit and must have a longer service life, convenient mounting means and the ability to operate consistently under repeated adjustments of the shaft. The modular construction utilized in the structure of the present invention permits mass production of either of the two types of variable resistors referred to above.

The primary object of the present invention is, therefore, to provide a variable resistor of modular construction which can be utilized in a broad range of applications.

A further object of the present invention is to provide a variable resistor of the type referred to in which a metal housing accommodates a full cup-shaped insulator, the insulating cup carrying locating abutments or indentations for the terminals, the wire wound resistor element and stops for orienting and limiting rotation of the rotor.

A further object of the present invention is to provide a variable resistor assembly of the type referred to utilizing a one-piece wiper or movable element structure for either two terminal or three terminal types of control.

A further object of the present invention is to provide a variable resistor assembly of the shaft actuated type in which the shaft is supported throughout axial length of the rotor.

A further object of the present invention is to provide a variable resistor structure which can be converted to a shaft actuated type by inserting a shaft within the rotor the structure and support of the rotor being such as to permit insertion of the shaft at either end of the rotor.

The full nature of the invention will be understood from the accompanying drawings and the following description and claims.

FIG. 1 is a perspective view of a portion of the structure of the present invention.

FIG. 2 is a fragmentary side View of a portion of the wire wound resistance element illustrating the terminal structure.

FIG. 3 is a view similar to FIG. 2 but showing the opposite side of the terminal structure and the resistor.

FIG. 4 is a top plan view of the insulating cup which is part of the structure shown in FIG. 1.

FIG. 5 is a side view of the rotor component.

FIG. 6 is a top plan view of the rotor shown in FIG. 5.

FIG. 7 is a perspective view of the contactor or wiper arm prior to its assembly on the rotor.

FIG. 8 is a side view of the rotor and contactor assembly.

FIG. 9 is a top plan view of an assembled structure of the three terminal type.

FIG. 10 is a sectional view taken generally along the line 10-10 of FIG. 9.

FIG. 11 is a side sectional view similar to FIG. 10 but illustrating the two terminal type of structure.

FIG. 12 is a side view of a shaft adapted for insertion into the axial aperture in the rotor.

FIG. 13 is an end view of the shaft of FIG. 12.

FIG. 14 is a side view of a dual assembly formed from the structure of the present invention.

FIG. 15 is a side view of a modified form of the structure of the present invention which utilizes an end plate carrying an integral bushing for mounting the control on a supporting panel.

Referring initially to FIGS. 1-10, the structure of the present invention includes a cup-shaped, metal housing 10 which is closed at one end and open at the other. The housing is provided with a cut-away section 1 1 at its open en Nested within the housing is an insulating cup 12 which is molded of suitable insulating material and provided with an axial aperture 13 which registers with a correspondin ly sized aperture in the closed end of the housing It The marginal area of the cup 12 is formed to provide an arcuate boss 14 which is accommodated in the cut-away portion 11 in the housing and serves to orient the cup within the housing. The inner surface of the cup side wall is provided with two, spaced bosses or stops 16 which extend the length of the cup and cooperate with abutments or shoulders on the rotor structure to be subsequently described.

The boss 14 is slotted for a portion of its depth at 17 (FIG. 4) 13 and 19. As may best be seen in FIG. 4, the base, or closed end of the cup 12 is provided with indentations 21 which extend adjacent the stops 16. Received within the cup is a resistance element 22 having terminal clips 23 secured to its ends and the clips bearing connecting tabs 24 which are bent radially outwardly to extend through the slots 17 and 19.

The resistance element 22 is formed by winding wire upon a strip of somewhat resilient insulating material. The wire ends are caught and securely held by means of ears 26 formed on the terminal clips 23 as may best be seen in FIGS. 2 and 3, the embracing relation of the clips with respect to the ends of the resistance element providing electrical contact with the element. The resistance element is located and rigidly held within the cup 12 by the extension of the thickness of the tabs 24 into the indentations 21 in the cup base, the resiliency of the resistance element serving to brace the base portion of the clips within the cup indentations.

Referring specifically to FIGS. -8, the rotor assembly includes a rotor 27 which is preferably molded of electrical insulating material. The rotor is provided with a shank portion 28 having an axial aperture 29 extending through the rotor, the aperture having cross-shaped configuration in cross section. A peripheral flange 31 is provided on the rotor, the flange being tilted with respect to the axis of the rotor shank. An arcuately shaped abutment 32 extends from the rotor flange and, diametrically opposite the abutment 32 the flange is chordally slotted as indicated at 33. An axially extending boss 34 strengthens the fiange area adjoining the slots 33.

The wiper arm or contacting element 36 is shown in FIG. 7, the element being shown in its free state and prior to its installation upon the rotor. The element 36 is formed of a generally figure eight configuration and includes a semi-annular portion 37 joined to a further semiannular portion 38 by means of intermediate, closely spaced legs 39. The portion 38 is disposed in a plane normal to the plane of the portion 37 and the portion 38 is provided with an ear 4-1 which is adapted to ride upon the resistance element 22. The portion 38 is further provided with bosses or abutments 42 extending from the underface of the legs making up portion 38.

The element 36 is assembled on the rotor 27 as indicated in FIG. 8. As there indicated, it will be noted that the legs 39 are disposed within the slots 33 and the portion 37 and 38 accommodate the shank portion of the rotor. The resiliency of the junction between the portion 37 and the legs 39 serve to urge the inner margin of the portion 37 against the surface of the rotor shank thereby locking the contacting element 35 upon the rotor. The marginal area 40 of the portion 37 is available for making contact with a further component of the structure to be subsequently described.

Received on the shank portion 28 of the rotor is a third terminal member 34 (FIGS. 9 and having an annular portion a encircling the rotor shank. The terminal member has a radially extending portion downwardly offset somewhat from the portion 30a and extending through the central slot 18 in the cup 12. As illustrated in FIG. 10 the marginal area 40 of the contacting element portion 37 engages and makes electrical contact with the annular portion m of the terminal 30.

A washer 46, formed of phenolic resin or ot er electrical insulating material overlies the terminal portion 30a.

As will be evident from FIG. 10 the end of the rotor shank 28 adjacent the ear 41 extends through the registering apertures in the cup 12 and housing 10. When so positioned and supported the contacting ears 41 on the element 36 engage the resistance element 22. It should further be noted that the spaced bosses 42 formed in the annular portion 33 of the element 36 ride upon the upper face of the end wall of cup 12. These bosses 42 act as fulcrurns for the contacting element portions 38.

As may be seen in FIG. 1B the open ends of the housing lid and cup 12 are closed by means of an end plate 4-3 which may be held on the housing by means of ears extending from the housing and overlying the end plate. The end plate is provided with a central aperture which receives the end of the rotor adjacent the contacting element portion 37. The end plate may be formed of metal as indicated in FIG. 10 and, in this case, the insulating washer 46, interposed between the underface of the end plate and the marginal area 40 of contacting element portion 37, prevents electrical contact of the element 36 with the end plate. The end plate may be provided with means for mounting the control on a supporting panel, such means taking the form of mounting cars 47. It will be obvious that other means for supporting the control on a panel or on a printed circuit board might be provided in place of the cars 47. Such alternate arrangements might include mounting ears extending outwardly from the end plate. it will be evident that the three terminal structure illustrated in FIG. 10 might be altered so as to eliminate the center terminal by grounding the element 36 to the end plate 43, the end plate itself thus serving as a third terminal. This modification may be accomplished, as shown in FIG. 11, by replacing the insulating washer 46 with a metallic or other electrically conducting washer 46a, and omitting terminal member 3% from the assembly. The washer 46a is somewhat thicker than the insulating washer 46 which it replaces since washer 46a must also replace, in thickness, the annular portion 36:: of terminal 3%. When so assembled, it will be evident that the marginal area 40 of the element 36 will resiliently engage the underface of the washer 46a and through the washer will have electrical continuity with the end plate 43.

The structure of FIGS. 9 and 10 may be adjusted by inserting a screwdriver or similar tool in the aperture 29 in the rotor and rotating the rotor assembly. This type of operation is satisfactory where the structure is to be used as a sensitivity control of the type mentioned above. Where the structure is to be used in applications requiring shaft adjustment, a shaft structure of the type shown in FIGS. 12 and 13 is utilized.

The shaft is indicated at 48 in FIG. 12 and is circular in cross section throughout the major portion of its length. The shaft is preferably formed of a somewhat resilient electrical insulating material such as nylon. At one end the shaft is formed to provide a portion 4-9 which is cross shaped in cross-sectional configuration, this portion of the shaft being sized so as to have a sliding fit within the aperture 23 in the rotor. One section 51 of the portion 49 extends beyond the adjacent section 52 and is bifurcated and the ends are provided with radially extending abutments 53. It should be noted that the spacing between the abutments 53 and the terminus of portion 49 of the shaft is such that upon insertion of this portion of the shaft into the rotor aperture 29 the abutments 53 will engage the outer end of the rotor as will be apparent from FIG. 15. Since the section '52 of the shaft portion 49 is foreshortened with respect to the section 51, the bifurcated end of the section 51 may give inwardly somewhat as the shaft is inserted into the rotor aperture. When the shaft is in place as shown in FIG. 15 it cannot be withdrawn except by compressing the bifurcated end of the shaft and again withdrawing it from the aperture.

Referring again to FIG. 15, it will be noted that, as an alternate construction, the end plate, indicated at 54 in FIG. may be molded or otherwise formed so as to include an integral bushing structure 56 accommodating a nut 57. The bushing and nut permit the control to be mounted on a panel with the bushing extending through an appropriately sized aperture in the panel (not shown). Referring to PEG. 14, it will be evident that two or more of the controls may be disposed in stacked relation and held therein by any suitable means such as the retainer 58. When this ganged type of assembly is used, the shaft portion 49 is dimensioned so as to extend completely through the axially aligned apertures in the control rotors.

From the foregoing it will be evident that the structure described permits several types of variable resistors to be formed with a minimum addition and interchange of parts. The structure of the contacting element 36 and its mounting on the rotor are such that the portion 38 fulcrums at the side of the rotor remote from the contact ear 41. Excellent compliance to the variations in the surface area of the winding 22 and proper contact pressure are maintained. The rigidity of the element 36 in a plane transverse to the axis of the rotor is relatively great. This rigidity is obtained because the element 36 is a double-armed structure and is restrained within the spaced slots 33 on the rotor. This arrangement further prevents the contacting element 36 from winding up or distorting in a horizontal plane and then jumping across a small area until the sideward distortion is again built up. Elimination of this winding up of the contacting element provides smoothness of operation and a good resettability factor.

The wrap around arrangement of the terminal clips 23 on the resistance element 22 eliminates the presence of small lengths of wire, which might escape trimming or removal. It will be evident that the presence of such pieces of wire might short out portions of the resistance element or otherwise render the unit defective. In the structure described the wrap around arrangement serves to effectively trap the loose ends of the wire forming the resistance element and the relatively large area of contact between the terminal clips and the wire turns increases the possibility of maintaining multiple electrical contact between the terminal clips and the wire winding. Since no rivet aperture is required in the Winding core the mechanical strength of the core is not weakened at the terminals and there is therefore less danger of the wire or the core being distorted or ruptured by forces applied to the terminal clip tabs 24.

The arrangement whereby shaft 48 is accommodated in the axial rotor aperture permits the shaft to be inserted from either end of the control. Since the shaft is in effect fluted and the rotor aperture is correspondingly formed, the extensive contact surfaces of the flute against the rotor provide large resistance to shear and permits the use of relatively high torques such as might be obtained when a relatively large knob is mounted on the shaft 48. The shaft is supported throughout the length of the rotor and misalignment or play in the shaft is thereby minimized.

In certain applications stops are required which limit the freedom of adjustment of the control, that is, the sector through which the rotor can be turned. Such stops of various sizes can be easily formed by changing the arcuate length of the abutments 32 on the rotor 27. The rotor itself is journaled at the base of the housing 10 and in the end plate 43 and, since it is thus held at spaced areas, the rotor cannot vary in its movement from a constant axis. The pressure of the contacting car 41 against the resistance element 22 is thus maintained relatively constant and wear spots on the resistance element are eliminated.

While the invention has been disclosed and described in some detail in the drawings and foregoing description, they are to be considered as illustrative and not restrictive in character, as other modifications may readily suggest themselves to persons skilled in this art and within the broad scope of the invention, reference being had to the appended claims.

What is claimed is:

l. A variable resistor comprising a metal housing having an open end and a closed end, a cup-shaped member formed of electrical insulating material nested within said housing with the 'base of the cup-shaped member adjacent the closed end of the housing, said base and closed end having registering apertures therein, said housing having a cut-away portion extending along its margin, an integral boss on said cup-shaped member extending into said cut-away portion for locating the member within the housing, a resistance element including a wire wound on a flexible insulating material and having terminal clips attached to the ends thereof, said resistance element being disposed around an inside wall of said cupshaped member and being circumferentially located by the terminal clips extending into indentations in the base of said member, said clips having terminal tabs extending radially outwardly through slots in the integral boss and through a boss extending radially inwardly from an inside wall of said cup-shaped member, a rotor having a cylindrical shank portion rotatably mounted in the aperture in said base and having a peripheral flange tilted with respect to the axis of the shank portion and having an arcuate abutment thereon extending to a radius from said axis in engageable relationship to said inwardly extending boss to limit extent of rotation of said rotor, said flange having a chordal slot therein on a side of said flange opposite said abutment, a resilient wiper member including a resistance element contacting ear disposed at the apex of a generally heart-shaped portion received on the shank of said rotor and lying generally in a plane perpendicular to the axis of said shank and having bosses therein in sliding engagement with said base, said wiper member having legs integral with said heart-shaped portion and lying in a plane normal to that of said heartshaped portion and received in the chordal slots in said flange, said Wiper member further having a semi-annular portion integral with said legs and received on said shank and lying predominantly in a plane tilted with respect to the axis of said shank, a conductor having a generally annular portion with an aperture therein, said annular portion encircling the rotor shank and engaging said wiper, said conductor having an integral terminal tab extending radially outwardly through slots in the inte gral boss and the inwardly extending boss, an aperture through said rotor having at least a portion with cruciform cross section, an end plate fastened to said housing and closing said cup-shaped member, said end plate having an aperture therethrough to receive the shank of said rotor, an insulating washer disposed between said end plate and said conductor to insulate the conductor from said end plate and being of a thickness whereby said end plate retains said conductor in sliding engagement with said wiper member.

2. A variable resistor bank comprising: a first variable resistor having a metal housing having an open end and a closed end, a cup-shaped member formed of electrical insulating material nested within said housing with the base of the cup-shaped member adjacent the closed end of the housing, said base and closed end having registering apertures therein, said housing having a cut-away portion extending along its margin, an integral boss on said cup-shaped member extending into said cut-away portion for locating the member within the housing, a resistance element including a wire wound on a flexible insulating material and having terminal clips attached to the ends thereof, said resistance element being disposed around an inside wall of said cup-shaped member and abutting the base and being eircumferentially located by aeeaoaa the terminal clips extending into recesses in spaced bosses extending radially inwardly from the inside wall of said cup-shaped member and by the terminal clips extending into indentations in the base of said member, said clips having terminal tabs extending radially outwardly through slots in the integral boss and the spaced bosses, a rotor having a cylindrical shank portion rotatably mounted in the aperture in said base and having a peripheral flange tilted with respect to the axis of the shank portion and having an arcuate abutment thereon extending to a radius from said axis in engageable relationship to said spaced b sses to limit extent of rotation of said rotor, said flange having a chordal slot therein on a side of said flange opposite said abutment, a resilient wiper member including a resistance element contacting ear disposed at the apex of a generally heart-shaped portion received on the shank of said rotor and lying generally in a plane perpendicular to the axis of said shank, said portion having a low section modulus for high rigidity in said plane and having bosses therein in sliding engagement with said base on a side of the rotor opposite said ear to thereby provide a fulcrum remote from said ear, said wiper member having legs integral with said heart-shaped portion, said legs lying in a plane normal to that of said heart-shaped portion and received in the chordal slots in said flange, said wiper member having a semi-annular portion integral with said legs and received on said shank and lying predominantly in a plane tilted with respect tothe axis of said shank, the resiliency of said wiper member engaging it firmly to said rotor, an aperture through said rotor having at least a portion with cruciform cross section, an end plate fastened to said housing closing said cup-shaped member, said end plate having an aperture therethrough to receive the shank of said rotor, and a shaft having a portion of circular cross section, an adjacent portion of cruciform cross section to fit the aperture through the rotor shank and a bifurcated portion having terminating abutments to engage the shank portion of said rotor for axial retention of the shaft in the rotor; and a retainer of semicylindrical form receiving and fastening to said first variable resistor a second variable resistor like the first, the bifurcated portion of the shank passing through both rotors.

3. A variable resistor bank comprising: a first variable resistor having a metal housing having an open end and a closed end, a cup-shaped member formed of electrical insulating material nested within said housing with the base of the cup-shaped member adjacent the closed end of the housing, said base and closed end having registering apertures therein, said housing having a cut-away portion extending along its margin, an integral boss on said cup-shaped member extending into said cut-away portion for locating the member within the housing, a resistance element including a wire wound on a flexible insulating material and having terminal clips attached to the ends thereof, said resistance element being isposed around an inside wall of said cup-shaped member and abutting the base and being circumferentially located by the terminal clips extending into recesses in spaced bosses extending radially inwardly from the inside wall of said cup-shaped member and by the terminal clips extending into indentations in the base of said member, said clips having terminal tabs extending radially outwardly through slots in the inte ral boss and the spaced bosses, a rotor having a cylindrical shank portion rotatably mounted in the aperture in said base and having a peripheral flange tilted with respect to the axis of the shank portion and having an arcuate abutment thereon extending to a radius from said axis in engageable relationship to said spaced bosses to limit extent of rotation of said rotor, said flange having a chordal slot therein on a side of said flange opposite said abutment, a resilient wiper member including a resistance element contacting ear disposed at the apex of a generally heart-shaped portion received on the shank of said rotor and lying generally in a plane perpendicular to the axis of said shank, said portion having a low section modulus for high rigidity in said plane and having bosses therein in sliding engagement with said base on a side of the rotor opposite said ear to thereby provide a fulcrum remote from said ear, said wiper member having legs integral with said heart-shaped portion, said legs lying in a plane normal to that of said heart-shaped portion and received in the chordal slots in said flange, said wiper member having a semi-annular portion integral with said legs and receive-d on said shank and lying predominantly in a plane tilted with respect to the axis of said shank, the resiliency of said wi, er member engaging it firmly to said rotor, an aperture through said rotor having at least a portion with cruciform cross section, an end plate fastened to said housing and closing said cup-shaped member and having an aperture therethrough to receive the shank of said rotor, a conducting washer disposed between said end plate and said wiper member, said conducting washer encircling the rotor and contacting the resilient wiper member to retain the rotor axially and to ground said wiper member to said end plate, and a shaft having a portion of circular cross section, an adjacent portion of cruciform cross section to fit the aperture through the rotor shank and a bifurcated portion having terminating abutments to engage the shank portion of said rotor for axial retention of the shaft in the rotor; and a retainer of semi-cylindrical form receiving and fastening to said first variable resistor a second variable resistor like the first, the bifurcated portion of the shank passing through both rotors.

4. A variable resistor comprising a metal housing having an open end and a closed end, a cup-shaped member formed of electrical insulating material nested within said housing with the base of the cup-shaped member adjacent the closed end of the housing, said base and closed end having registering apertures therein, said housing having a cut-away portion extending along its margin, an integral boss on said cup-shaped member extending into said cut-away portion for locating the member within the housing, a resistance element including a wire Wound on a flexible insulating material, said resistance element being disposed around an inside wall of said cup-shaped member and abutting the base, terminal clips carried on the ends of said resistance element, said resistance element being circumferentially located by extension of said terminal clips into recesses in spaced bosses extending radially inwardly from the inside Wall of said cup-shaped member and by extension of the terminal clips into indentations in the base of said member, said clips having terminal tabs extending radially outwardly through slots in the integral boss and the spaced bosses, a conductor having a generally annular portion and having an integral terminal tab extending radially outwardly through a slot in the integral boss and a slot between the spaced bosses, a rotor having a cylindrical shank portion rotatably mounted in the aperture in said base and having a peripheral flange tilted with respect to the axis of the shank portion and having an arcuate abutment thereon extending to a radius from said axis in engageable relationship to said spaced bosses to limit extent of rotation of said rotor, said flange having a chordal slot therein on a side of said flange opposite said abutment, a resilient Wiper member including a resistance element contacting ear disposed at the apex of a generally hear -shaped portion, said portion being re ceived on the shank of said rotor and lying generally in a plane perpendicular to the axis of said shank, bosses formed on said portion adapted to slidably engage said cup-shaped member base, said wiper member having legs integral with said heart-shaped portion and lying in a plane normal to that of said heart-shaped portion and 9 received in the chordal slots in said rotor flange, said wiper member further having a semi-annular portion integral with said legs and received on said shank and lying predominantly in a plane tilted with respect to the axis of said shank the resiliency of said wiper member engaging it firmly to said rotor, an aperture through said rotor having at least a portion with cruciform cross section, an end plate fastened to said housing and closing said cup-shaped member, said end plate having an aperture therethrough to receive the shank of said rotor, an insulating washer disposed between said end plate and said conductor to insulate the conductor from said end plate, and a shaft having a portion of circular cross section, an adjacent portion of cruciform cross section to fit the aperture through the rotor shank and a bifurcated portion having terminating abutments to engage the shank portion of said rotor for axial retention of the shaft in the rotor.

5. In a variable resistor a contact bearing member comprising: a rotor having a shank portion, said shank portion having a tilted peripheral flange and an arcuately shaped abutment extending therefrom and aligned chordal slots in said flange diametrically opposite the abutment; and a contact member having a pair of semi-annular portions joined by spaced legs, said semi-annular portions being received on the shank of said rotor and resiliently bearing thereon, said legs extending through said chordal slots and gripping the end faces of said slots to resist forces tending to skew said contact member with relation to the axis of said rotor shank.

6. In a variable resistor, a housing having a rotor extending therethrough and journalled for rotation in opposed end walls of the housing, said rotor having a cruciform bore extending completely therethrough, a control shaft for rotation of said rotor having a portion at one of its ends of substantially the same length as said rotor and formed by web sections providing a cruciform cross-section of said shaft portion to permit insertion thereof into said rotor from either end of the rotor, two opposed web sections of said shaft portion extending beyond the other web sections to weaken the tip of said shaft portion with respect to forces transverse to the axis of said shaft, and radially outwardly extending abutments carried by said extending opposed web sections, whereby upon insertion of said shaft portion into said rotor bore said opposed web sections are initially deformed radially inwardly to accommodate the abutments carried thereby in the rotor bore, the return of said opposed web sections to their underfcrmed position carrying said abutments into locking engagement with the end face of said rotor as the abutments clear the rotor bore to prevent withdrawal of said shaft from said rotor.

7. A variable resistor comprising a cup-shaped member of electrical insulating material, the base of said cup-shaped member having an aperture therein, an integral sidewardly extending boss on said cup-shaped member, a resistance element including a wire wound on a flexible insulating material and having terminal clips attached to the ends thereof, said resistance element being disposed around an inside wall of said cup-shaped mem her and being circumferentially located by the terminal clips extending into indentations in the base of said member, said clips having terminal tabs extending radially outwardly through slots in the integral boss and through a boss extending radially inwardly from an inside wall of said cupshaped member, a rotor having a cylindrical shank portion rotatably mounted in the aperture in said base and having a peripheral flange tilted with respect to the axis of the shank portion and having an arcuate abutment thereon extending to a radius from said axis in engageable relationship to said inwardly extending boss to limit extent of rotation of said rotor, said flange having a chordal slot therein on a side of said flange opposite said abutment, a resilient wiper member including a resistance element contacting ear disposed at the apex of a generally heart-shaped portion received on the shank of said rotor and lying generally in a plane perpendicular to the axis of said shank and having bosses therein in sliding engagement with said base, said wiper member having legs integral with said heart-shaped portion and lying in a plane normal to that of said heartshaped portion and received in the chordal slots in said flange, said wiper member further having a semi-annular portion integral with said legs and received on said shank and lying predominantly in a plane tilted with respect to the axis of said shank, a conductor having a generally annular portion with an aperture therein, said annular portion encircling the rotor shank and engaging said wiper, said conductor having an integral terminal tab extending radially outwardly through slots in the integral boss and the inwardly extending boss, an aperture through said rotor having at least a portion with cruciform cross-section, an end plate closing said cupshaped member, said end plate having an aperture therethrough to receive the shank of said rotor, an insulating washer disposed between said end plate and said conductor to insulate the conductor from said end plate and being of a thickness whereby said end plate retains said conductor in sliding engagement with said wiper member.

References Cited in the file of this patent UNITED STATES PATENTS 2,213,078 Stoekle Aug. 27, 1940 2,266,188 Foley et al. Dec. 16, 1941 2,389,750 Turner et a1 Nov. 27, 1945 2,406,503 Miller Aug. 27, 1946 2,446,417 Hastings Aug. 3, 1948 2,454,816 Levy Nov. 30, 1948 2,737,560 Mucher Mar. 6, 1956 2,790,882 Siegel Apr. 30, 1957 2,804,528 Rapisarda Aug. 27, 1957 2,814,705 Eshelman Nov. 26, 1957 

1. A VARIABLE RESISTOR COMPRISING A METAL HOUSING HAVING AN OPEN END AND A CLOSED END, A CUP-SHAPED MEMBER FORMED OF ELECTRICAL INSULATING MATERIAL NESTED WITHIN SAID HOUSING WITH THE BASE OF THE CUP-SHAPED MEMBER ADJACENT THE CLOSED END OF THE HOUSING, SAID BASE AND CLOSED END HAVING REGISTERING APERTURES THEREIN, SAID HOUSING HAVING A CUT-AWAY PORTION EXTENDING ALONG ITS MARGIN, AN INTEGRAL BOSS ON SAID CUP-SHAPED MEMBER EXTENDING INTO SAID CUT-AWAY PORTION FOR LOCATING THE MEMBER WITHIN THE HOUSING, A RESISTANCE ELEMENT INCLUDING A WIRE WOUND ON A FLEXIBLE INSULATING MATERIAL AND HAVING TERMINAL CLIPS ATTACHED TO THE ENDS THEREOF, SAID RESISTANCE ELEMENT BEING DISPOSED AROUND AN INSIDE WALL OF SAID CUPSHAPED MEMBER AND BEING CIRCUMFERENTIALLY LOCATED BY THE TERMINAL CLIPS EXTENDING INTO INDENTATIONS IN THE BASE OF SAID MEMBER, SAID CLIPS HAVING TERMINAL TABS EXTENDING RADIALLY OUTWARDLY THROUGH RADIALLY INWARDLY FROM AN AND THROUGH A BOSS EXTENDING RADIALLY INWARDLY FROM AN INSIDE WALL OF SAID CUP-SHAPED MEMBER, A ROTOR HAVING A CYLINDRICAL SHANK PORTION ROTATABLY MOUNTED IN THE APERTURE IN SAID BASE AND HAVING A PERIPHERAL FLANGE TILTED WITH RESPECT TO THE AXIS OF THE SHANK PORTION AND HAVING AN ARCUATE ABUTMENT THEREON EXTENDING TO A RADIUS FROM SAID AXIS IN ENGAGEABLE RELATIONSHIP TO SAID INWARDLY EXTENDING BOSS TO LIMIT EXTENT OF ROTATION OF SAID ROTOR, SAID FLANGE HAVING A CHORDAL SLOT THEREIN ON A SIDE OF SAID FLANGE OPPOSITE SAID ABUTMENT, A RESILIENT WIPER MEMBER INCLUDING A RESISTANCE ELEMENT CONTACTING EAR DISPOSED AT THE APEX OF A GENERALLY HEART-SHAPED PORTION RECEIVED ON THE SHANK OF SAID ROTOR AND LYING GENERALLY IN A PLANE PERPENDICULAR TO THE AXIS OF SAID SHANK AND HAVING BOSSES THEREIN IN SLIDING ENGAGEMENT WITH SAID BASE, SAID WIPER MEMBER HAVING LEGS INTEGRAL WITH SAID HEART-SHAPED PORTION AND LYING IN A PLANE NORMAL TO THAT OF SAID HEARTSHAPED PORTION AND RECEIVED IN THE CHORDAL SLOTS IN SAID FLANGE, SAID WIPER MEMBER FURTHER HAVING A SEMI-ANNULAR PORTION INTEGRAL WITH SAID LEGS AND RECEIVED ON SAID SHANK AND LYING PREDOMINANTLY IN A PLANE TILTED WITH RESPECT TO THE AXIS OF SAID SHANK, A CONDUCTOR HAVING A GENERALLY ANNULAR PORTION WITH AN APERTURE THEREIN, SAID ANNULAR PORTION ENCIRCLING THE ROTOR SHANK AND ENGAGING SAID WIPER, SAID CONDUCTOR HAVING AN INTEGRAL TERMINAL TAB EXTENDING RADIALLY OUTWARDLY THROUGH SLOTS IN THE INTEGRAL BOSS AND THE INWARDLY EXTENDING BOSS, AN APERTURE THROUGH SAID ROTOR HAVING AT LEAST A PORTION WITH CRUCIFORM CROSS SECTION, AN END PLATE FASTENED TO SAID HOUSING AND CLOSING SAID CUP-SHAPED MEMBER, SAID END PLATE HAVING AN APERTURE THERETHROUGH TO RECEIVE THE SHANK OF SAID ROTOR, AN INSULATING WASHER DISPOSED BETWEEN SAID END PLATE AND SAID CONDUCTOR TO INSULATE THE CONDUCTOR FROM SAID END PLATE AND BEING OF A THICKNESS WHEREBY SAID END PLATE RETAINS SAID CONDUCTOR IN SLIDING ENGAGEMENT WITH SAID WIPER MEMBER. 